Disclaimer: I'm not using this to suggest changes to Yamato in game right now.

Through my Googling, I found a rather interesting article that documents why the Yamato's torpedo defense system was flawed, I pasted the link and article below if you want to open and read the whole thing. But I'll try to provide a TL;DR version.

During the design for Yamato, the decision was made to use reliable, but inefficient boilers and machinery. Consequently, it took 12 boilers to produce the 150,000 SHP that the ship was designed for (compare to 130,000 SHP with 8 boilers on the South Dakota, and 212,000 SHP with 8 boilers on Iowa). Another design driver the Yamato was to make the armored citadel short to save weight, and they accomplished this by arranging the boilers to be 4 abreast of each other in 3 rows, which made the ship very wide. This is why despite the Yamato's large beam, the torpedo defense system depth wasn't actually very high, at around 5.1 m abreast of the machinery spaces, which is actually shallower than North Carolina and Iowa systems.

The second problem with the torpedo defense is that one of the bulkheads of the system is the lower armor belt, since the Yamato had her armor belt extend all the way down to the keel, similar concept to the South Dakota and Iowa. The problem here is that the joint between the upper face hardened belt and the lower homogeneous belt had a very poorly designed, with the traverse shear strength dependent on vertically aligned rivets. Contrast this with the South Dakota (and Iowa) method, where the upper and lower belt are keyed together. Also, unlike the British and Americans, the Yamato's torpedo system did not have any liquid compartments. It's not really clear why the Japanese decided to not do this, the author speculates it may be for lower draft.

Essentially, these problems meant that the Yamato's torpedo defense was not nearly as strong as hoped, and why the Yamato took so much flooding from just one torpedo.

Just before dawn on Christmas day 1943 the Gate class submarine USS Skate was patrolling about 180 nautical miles northwest of Truk. The main operational base of the Japanese Combined Fleet, when her surface search radar picked up three contacts at 23,0(X) yards steaming southeast at 19 knots. As the contacts closed, they showed themselves as one large vessel and two smaller ones, the latter apparently being escorting destroyers. In the growing light of the tropical dawn, Skates Captain, McKinney, dived his boat although he lay to the west in the darkest part of the horizon and fired a salvo of four torpedoes at the largest target. With his submerged speed limited to 10 knots he had no real alternative Course of action and although he was unable to identify it he was rewarded by the gratifying sound of one detonation. However, the ship did not stop and Skate continued her patrol unmolested and unaware that she was the first American vessel privileged to catch sight of the giant battleship Yamato, the pride of the Imperial Japanese Navy.

Such was the parlous state of the Japanese merchant marine, even at this stage of the war, that Yamato had been dispatched as a distinctly unusual fast transport from Truk to Japan on 12 December 1943. She had arrived at Yokosuka with out incident five days later and for the next three days was loaded with supplies and soldiers. With two escorting destroyers she then sailed for Truk and her meeting with Skate. Morison, in his official work on US naval operations in World War II, implied that she was on passage from Truk to Kavieng. In New Ireland when the attack was made but this is incorrect in both the light of Japanese records and the calculations of the distance and time involved.

After the attack, Yamato's speed was unimpaired and she continued on to Truk anchoring later the same day. Eventually, after a vacillating delay of five days, her cargo of troops and stores was off loaded. Any extension of her mission was cancelled. This may well have been a prudent decision because had she completed her sortie she would probably have been attacked by aircraft from two US carriers which were deployed to intercept just such traffic. As her subsequent experiences during the Battle of Leyte Gulf and in the South China Sea demonstrated, she had immense resilience under attack, but such an encounter in a less critical operation would have been, to say the least, ill-judged.

Fortunately, nobody was killed in the attack and as her cargo was being off loaded divers were sent down to inspect the damage and make temporary repairs. Truk had always been more of an anchorage than a fleet base and had few repair facilities, despite allied assumptions to the contrary, and so a return to Japan was inevitable after the torpedo attack. With one escorting destroyer, Fujinami, she sailed from Truk for the last time on 10 January 1944 and docked at Kure six days later. It was to be four months before the damage was repaired and a minor refit completed, though, happily for Japan, she missed no significant action.

Such a catalogue of events is not remarkable. Any ship at sea in wartime is likely to he open to submarine attack and the hit on Yamato was simply one more example to add to many others. What was far more significant for the leaders of the Imperial Japanese Navy was the extent of the damage. The explosion had occurred on the starboard side beneath the after l8in main triple gun turret. Quoting from her Captains report to the Navy Ministry the damage was as follows:

"A hole about 16ft (5m) deep extending downwards from the top of the bulge connection and 82ft (25m) in length between frames 151 and 173. Water flooded into No 3 turret upper magazine from a small hole in the longitudinal bulkhead caused by caving in of the waterline armor"

Put simply, her underwater defenses had been breached by a single torpedo and she had shipped over 3000 tons of water, something which her designers had worked assiduously to avoid. The resultant concern deepened when it was learnt that the torpedo had been running shallow and had struck only four feet below the surface, where the explosive effect, which increases with the depth of water, had not been particularly great. What is interesting is how and why the design failed on a ship which the Japanese had always intended to he the pinnacle of battleship excellence and one certainly capable of stopping a single torpedo. From the time the, Japanese Naval General Staff ordered the Bureau of Naval Construction to study

such a proposal in the autumn of 1934 it was clear the vessel would he enormous since the only sure way of building in superiority in the three key elements of speed, firepower and protection, was to increase the size of the vessel. The first calculations of her principal designers, Yuzura Hiraga and Keiji Fukuda, proved too ambitious even for the Admirals of the Naval General Staff It was speed that was sacrificed since the length and depth of the hull proposed, which were vital prerequisites for high speed, would simply not fit Japanese parts without unacceptable additional expense. On the other hand, a shorter and beamier hull which was still thought likely to confer a speed comparable with future US ships was not without compensations which they did their best to exploit.

Despite this she still had a draft of 10.8m when fully loaded and some dredging was required at the approaches to naval bases and dry docks. Nonetheless, the final trial displacement of 69,100 tons was still close to twice the size of any operational battleship at the time, though the battleships of other navies were naturally following the same inexorable trend, This final design remained, despite the compromise, well balanced. Just over 58 percent of displacement was consumed by the three key considerations:

33.2 percent or 22,895 tons being allocated to armor, 16.9 percent or 11,661 tons to weaponry and 7.7 percent or 5300 tons to machinery. The only slight deviation from what might be thought the norm was that the figure for machinery was a little low, the accompanying reduction in speed required for the weight saved to he used for protection. It is the underwater element of this defense which must now be considered.The ideal of all-round protection had long since been abandoned as shell and torpedo attack had proved too destructive. Along with other navies the Japanese adopted the 'all or nothing' principle; protection was limited to those areas vital for survival and for fighting; in short, the main machinery and gun turrets. The result was an armored central raft which left the bow and stern sections virtually unprotected. The smaller an area this raft represented the stronger could he the armor, and this was not of inconsiderable importance given that a single 12in cube of steel plate weighed a quarter of a ton. In the case of Yamato her great beam, which at the maximum was 127.7ft (38.9m), proved a great boon because her four main turbines and their associated boiler rooms could all be placed side by side across her hull. As a consequence, the area to be shielded shrank to a surprisingly short section of the hull, amounting to just 53.3 percent of the waterline length of 839ft (256m). This was a great achievement and her broad hull also conferred sufficient buoyancy for her to float even if all the unprotected spaces were left open to the sea after enemy action.

Damage from the initial kinetic energy of incoming shellfire could best be minimized by thick armor plate with a hardened exterior, hut such a system could never hope to defeat a torpedo's explosive charge of several hundred pounds detonating in direct contact with it and amplified by the surrounding water. Matters could actually he made worse since the heavy armor tended to fracture and the broken shards could rip deep into the hull. Volume was the best protection against torpedoes since it allowed for the expansion of the explosive gases while the remaining force rapidly dissipated with distance. There was never enough internal volume in a hull to provide much space for this and designers generally had to be satisfied with providing the minimum. In the case of Yamato the constraints were severe despite her great beam because of her chosen machinery layout. This was exacerbated by the choice of a reliable but bulky set of boilers, which ran at relatively low pressure. They were used because replacement beneath the 200mm armored deck would have proved extremely difficult hut the corollary was a narrower torpedo defense.

The width of this around her machinery spaces was on average 5.1m, and was narrower than that of almost all her contemporaries in other navies despite her displacing considerably more. Two examples will suffice to illustrate this. The American North Carolina, on a displacement calculated in a comparable manner at 45,298 tons, had a system 5.6m deep, while the German Scharnhorst on only 35,398 tons still managed a depth of 5.4m. For Yamato, it was therefore essential that within the comparatively narrow space remaining the best possible arrangement was used.

In order to counter a torpedo explosion, a space outside the true hull was required which would be strong enough to detonate the weapon well away from a stronger yet flexible main bulkhead beneath. The Japanese developed empirical formulae to determine the thickness of protective bulkheads and bulges based on tests with models and full scale systems. Once established they were then used with much confidence and for Yamato the main bulkhead was to be 75mm ducol steel. When a full scale plate of this was duly tested in 1939 against a blast of 400kg of TNT, the results were encouraging since it did not split open although its watertight integrity was lost.

Unfortunately, the designers also had to counter what was considered to be the great danger of long range plunging shell fire which might dive under the main armor belt and into the ship's vitals. The physical requirements for resisting the kinetic energy of shellfire and the explosive force of torpedoes could not be easily reconciled in a single system, but in Yamato there was not the room to separate one from the other. The enormous 410mm main belt was inclined on average at a 20 degree angle which increased the thickness of armor which any steeply falling shell would have to penetrate, and this angle conveniently provided space outboard for the anti-torpedo bulge without altering the form of the hull. The belt would have run into the 75mm anti-torpedo bulkhead below, but such was the fear of shell fire following tests on the underwater trajectories of projectiles that this was radically increased in thickness till, over the main machinery, it tapered from no less than 200mm down to the original 75mm at the ship's bottom.

Given a larger bulge outboard this main defense would have been far more formidable but by linking it to the main belt the bulge was only 3m wide at most at mid-draft. By comparison with foreign practice this placed it uncomfortably far forward thus failing to take full advantage of the limited depth available and compounding the weakness by reducing its ability to deform under pressure, just when such a feature was more essential. In the USN, the South Dakotas had a similar arrangement but they were designed within stringent Treaty constraints, a worry Yamato's designers did not have. In the US Montana class, a planned vessel of similar dimension to Yamato, the holding bulkhead was placed much deeper and not tied to the belt at all.

This late adoption of a thicker, lower bulkhead caused a new problem: how to join it to the main belt above without jeopardizing the great inherent strength of either half. The solution, as can be seen, was far too flimsy and relied for its transverse strength, which would be tested most in a torpedo strike, on the shearing resistance of tap and three-ply rivets. This was to prove the Achilles heel of the system.

The percentage of explosive force which would break on this flawed main defense did not rely only on the volume of the intervening outboard space. The composition of this space could be significant, and in all Yamato's foreign contemporaries part or all of the outboard void was tilled with liquid, generally fuel oil. This was not a fire risk and since it was incompressible it could spread and reduce the shock of any explosion, and in addition diminish the danger from splinters. The Imperial Navy were well aware of this system and thought liquid layers next to the main bulkhead were the best type, but like the Royal Navy, their primary teachers, they also experimented with using closed steel tubes which were packed into the outboard spaces to fulfill a similar function.

In practice they rusted and proved inefficient energy absorbers although in a Japanese report of 1936 their use was calculated to reduce 'the thickness of the protective plate to 70 percent generally'. For Yamato, even this expedient was dispensed with partly because of the chronic steel shortage exacerbated in large measure by her and her sister's construction, Although fuel oil was stored in the double bottom this was the only use of liquid and its defensive properties were not taken into any calculation. Yamato's outboard explosion chambers were left watertight and empty of anything more tangible than air.

Since the advantages of liquid loading were understood, this result is difficult to comprehend, despite assertions at the time that the heavy armor would be sufficient by itself. Pumping arrangements for such spaces could increase flooding since the valves between tanks were liable to fracture after an explosion. but since Yamato ~ range of 7200 nautical miles at 16 knots was low, taking into account the vast size of the Pacific. the extra storage would have proved beneficial in more senses than one. It has also been suggested that they needed to he left empty for possible use in counter flooding, and they were certainly equipped for this, and yet if they were partially filled, flooding with seawater on one side would have had less effect. It is possible that the need to keep her draft shallow influenced the decision. This is supported by the fact that a proposal to reduce the individual volume of compartments outside the citadel was rejected because the extra weight would have had an adverse effect on her draft.

Two longitudinal bulkheads were included between the main armor and the outboard main machinery spaces in order to contain any flooding and, in addition, the anti-torpedo bulkhead was thickened, The two bulkheads were designed to be capable of deforming without rupturing and, to add elasticity, the flooring was offset on opposite sides of the bulkhead, hut it was still too stiff and it could suffer little deflection without rupture, at least of butts and floor connections'. There was also a fear that because the fire rooms were closed, the air pressure inside the boiler rooms would he too great, and so the two inner defenses were braced still more by heavy beams placed transversely at the upper operating level. Any movement of the bulkheads, however, would simply cause them to be punctured by the beams permitting water to enter the fire rooms. Opposite the magazines forward and aft of the machinery such expedients were not required but there was only one holding bulkhead behind the main armor, reflecting the narrowing of the hull which confined internal volume still more. If this last over-rigid barrier was breached, internal flooding was inevitable.

This, in essence, is what happened when Skate's torpedo struck. Running shallow it hit the bulge where it was less than 2m wide and the main belt took most of the blast.

This did not fracture, hut the weak joint below did shear, indenting both sides into the ship by about I m. This in turn led to the last defense being holed as mentioned in her Captain's report. Had the torpedo been running deeper and hit closer to the suspect joint, damage would have been far greater. The resultant flooding caused a list of two to three degrees hut since the outboard voids were fitted with sea [edited] of 10in diameter, which could be operated remotely, counter flooding on the port side quickly put her hack on an even keel.

When these weaknesses were realized by the technical teams investigating the damage, they suggested that a new plate be installed across the lower corner of the upper void between the two inboard bulkheads and inclined at 40 degrees. This was proposed for the full length of the machinery spaces but it was hopelessly inadequate and in the event was only fitted in the region that had been damaged.

Of greater interest are the factors surrounding the decision taken in 1939 to increase the armor thickness of the side defenses, and accept what was always suspected to be a weak joint between it and the main belt. The importance of Yamato in prewar Japanese naval plans cannot he overestimated. The state economy could not hope to compete with that (if the USA in quantity, so quality and superior technology were, not for the first or last time, seen as the solution, and Yamato was the embodiment of this ambition. The navy had already constructed an elaborate and detailed plan to defeat the US Pacific Fleet, and it was intended that the big guns of the Combined Fleet would deliver the loop de grace. This planned scenario does much to explain why Yamato's designers changed emphasis towards favoring an anti-shell protective defense.

The unwillingness to wait for a suitable joint to he developed can also be understood in relation to the Imperial Navy's overall plans for the future. To establish her necessary technological lead, secrecy was vital to forestall any American response, but despite inordinate Japanese zeal some rumor of what was happening inevitably crossed the Pacific'. The US had, therefore, recommenced naval building and any delay in the construction of Yamatowould have sacrificed the Imperial Navy's slender lead.

Rivalry between the army and navy also played its part, not only over funding such items as expensive battleships, hut also in determining national policy. In such a climate delays in construction could have given the army the upper hand and so had to he avoided.

Two major ironies overhang this discussion. The obvious one is that all this time, effort and money spent on battleship construction was to prove virtually irrelevant. The future of naval warfare lay with carrier air power not the big gun. Both Yamato and her sister Musashi were to succumb to aerial attack, their main 18in guns virtually unused in anger. The second is that the torpedo fired by Skate was armed with a warhead of 635lb of a new explosive,'Torpex'. This had twice the explosive power of TNT and with its introduction in 1943 it upset, at a stroke. all the careful calculations on which Yamato's designers had labored for so long. It will be recalled that constraints were such that defenses could only ever he just sufficient: With the introduction of Torpex the most robust anti-torpedo system was likely to be breached. It was a pity that Yamato's design sacrificed underwater defense in depth when the threat in this sphere had increased so markedly. Nonetheless, even with the flaws discussed here her defenses were still powerful and her resilience under assault later amazed her American foes. However, her torpedo protection was without doubt the weakest element in an impressive design and it is not surprising that torpedoes were eventually to dispatch both vessels.

Yes. The TDS on the Yamato class didn't perform well in practice. I am not at home to check my books, but as I recall the steelwork was excessively rigid and poorly joined. When struck, the plates didn't give enough as a result torpedo hits could fail to penetrate, but the shock of the hits would displace steel plates (which weren't well joined as you mentioned) and let water, effectively defeating the system that way. That's how Yamato took 3,000 tons of water in from a single torpedo hit dead on her TDS. I vaguely recall that the Yamatos weren't particularly well compartmentalized for such large ships either.

The good news as I recall was that the ships had MASSIVE buoyancy reserves. They could flood almost all areas outside of the citadel area and stay barely afloat. I suspect that buoyancy reserve is the real reason why they survived as long as they did from the air attacks that did them in.

In fact, turboelectric propulsion is coming back, now called Integrated Electric Propulsion, like you see on the new Zumwalt-class DDGs and the upcoming Columbia-class SSBN, only that instead of fuel oil and steam turbines, it's gas turbines and nuclear reactor + steam respectively.

In fact, the H-39, which is the FDG in this game, uses diesel propulsion, which is why the funnels of that ship looks so unique compared to all the other BBs in game. The H-39/FDG is powered by 12 diesel engines (4 per shaft), which is why each of the 2 funnels have a cluster of 6 exhaust pipes. Diesels are taller and bulkier compared to steam but they have serious fuel efficiency advantages when cruising, which explains why the H-39 has such long range as designed. I'd imagine that diesels also start up and get up to power much quicker than steam, which requires the boilers to warm up first.

Imagine if that's in the game. While the FDG just steps on the gas and sails away, you in your Iowa are stuck in port waiting for the boilers to heat up.

Yep. Diesel will start quickly and also get much better range. It's biggest drawbacks are speed and acceleration. That was one of Graf Spee's few flaws and part of the reason why the Germans didn't use them on S&G. Existing diesels couldn't drive the ships fast enough.

Careful you are treading on dangerous ground, a couple redditors tried to skin me alive when I implied that the Yamato didnt have the absolute strongest TDS. Its a good read though +1.

They didn't. (Got home to my books now.) Postwar testing with armor plates from one of the Yamatos (I think it was Shinano's plates that were never installed) showed that the TDS (due to too much rigidity and poor joining) could actually be compromised by torpedoes carrying 600lb warheads. That is low enough that aircraft torpedoes can compromise it. The system was claimed to resist 880lbs. In a real world example, North Carolina was torpedoed by a Japanese submarine alongside her #1 turret and took on less than 1000 tons of water from the damage. (She purposely took on more water to counterflood.) Musashi got torpedoed a little forward of her #1 turret and took 3,000 tons of water. Add to this the fact that Japanese torpedoes were more powerful and the fact that a Yamato is almost twice the standard displacement of a North Carolina and you can see the difference in capability of the TDS and better subdivision. Yamato actually had worse subdivision than Nagato. (1147 compartments in Yamato vs. 1089 in Nagato despite Nagato being a little more than half the size.)

Note - Post-war a US naval commission examining Japanese equipment determined Yamato's armor was about 90% as effective as US and British armor due to poor cementing and poor heat treatment, making it very brittle.

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They didn't. (Got home to my books now.) Postwar testing with armor plates from one of the Yamatos (I think it was Shinano's plates that were never installed) showed that the TDS (due to too much rigidity and poor joining) could actually be compromised by torpedoes carrying 600lb warheads. That is low enough that aircraft torpedoes can compromise it. The system was claimed to resist 880lbs. In a real world example, North Carolina was torpedoed by a Japanese submarine alongside her #1 turret and took on less than 1000 tons of water from the damage. (She purposely took on more water to counterflood.) Musashi got torpedoed a little forward of her #1 turret and took 3,000 tons of water. Add to this the fact that Japanese torpedoes were more powerful and the fact that a Yamato is almost twice the standard displacement of a North Carolina and you can see the difference in capability of the TDS and better subdivision. Yamato actually had worse subdivision than Nagato. (1147 compartments in Yamato vs. 1089 in Nagato despite Nagato being a little more than half the size.)

Note - Post-war a US naval commission examining Japanese equipment determined Yamato's armor was about 90% as effective as US and British armor due to poor cementing and poor heat treatment, making it very brittle.

The American system of internal belt armor used on the Iowa and South Dakota utilized a different method of joining the upper and lower belt, which made it much stronger than the brittle system used to hold Yamato's upper and lower sections. The main failure of Yamato's system is that joint, as well as the fact that the entire bulge is filled with air, which does jack all to actually dissipate the force of the explosion of a torpedo. Yamato's system was the air filled (actually rather narrow) bulge, the lower belt, and then an extremely thin "splinter" bulkhead behind that before the machinery spaces. I honestly believe that the old rebuilt Nagato's had a stronger torpedo defense system as a whole than Yamato. The system itself was deeper, it had three large divisions, the outer layer of the bulge could hold oil, and the system had a 75 mm sandwich of curved plates along its entire length, increasing greatly in thickness around the magazines. Behind that was another oil bunker, with yet another 25 mm thick splinter bulkhead. Not only that, but the 75 mm plate was curved in a manner that would force some of the explosions energy up and outwards. I believe Nagato's had a good system, although another outboard liquid layer would have been nice.

Iowa and South Dakotas system had two outboard liquid layers, a void layer, the lower belt, and then another void with a 16 mm STS layer behind it (which increased to 25 mm around the magazines). It was also deeper than Yamato's, despite the ships being much narrower. The upper and lower belt were held via keying the plates, which is much more robust than the joints on Yamato. It disperses the stress on the support structure as a whole, rather than one tiny spot.

In terms of armor quality, its a bit nebulous. Post 1935 Class A had its face hardened too deeply, which while ideal versus cruiser caliber weaponry, caused a loss in performance against larger caliber shells. Realistically speaking, Class A was about 8-10% worse than British Cemented plates made at the same time, and Japanese cemented plates were 10-15% worse than Class A because of the opposite problem, having produced them with too shallow of a face. In terms of the actual ballistic qualities of various nations cemented armor, it goes something like this IIRC:

Italian=British>German>American>>Japanese=French (although very little is actually known about French armor properties, apart from it being generally very poor). The main advantage of Class A was that its quality control was bar none the best in the world, so it at least performed pretty uniformly no matter what.

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Not flooding the bulge was an intentional design decision to allow for more leeway during counter flooding without resorting to further flooding compartments.

Iowa and South Dakota both suffered the same "flaw" in hull plate rigidity.

4 hours ago, Tzarevitch said:

They didn't. (Got home to my books now.) Postwar testing with armor plates from one of the Yamatos (I think it was Shinano's plates that were never installed) showed that the TDS (due to too much rigidity and poor joining) could actually be compromised by torpedoes carrying 600lb warheads. That is low enough that aircraft torpedoes can compromise it. The system was claimed to resist 880lbs. In a real world example, North Carolina was torpedoed by a Japanese submarine alongside her #1 turret and took on less than 1000 tons of water from the damage. (She purposely took on more water to counterflood.) Musashi got torpedoed a little forward of her #1 turret and took 3,000 tons of water. Add to this the fact that Japanese torpedoes were more powerful and the fact that a Yamato is almost twice the standard displacement of a North Carolina and you can see the difference in capability of the TDS and better subdivision. Yamato actually had worse subdivision than Nagato. (1147 compartments in Yamato vs. 1089 in Nagato despite Nagato being a little more than half the size.)

Note - Post-war a US naval commission examining Japanese equipment determined Yamato's armor was about 90% as effective as US and British armor due to poor cementing and poor heat treatment, making it very brittle.

Apples and oranges. Musashi took the torpedo in the bow outside the protection zone of her torpedo bulkhead. NC took the hit into the bulkhead just forward of the turret which, ironically, still resulted in a penetration of the hull.

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The manner in which the lower belt section was constructed and attached to the structure of the hull precluded the same total failure and collapse as happened with Yamato's system.

This wasn't a forgone conclusion, it was merely an inherent chance of failure in the design, and it wasn't a "collapse" that was a concern. Its that the joining structure would be pushed inward through the hull from a blast. Yamato took 14-20 (depends on sources) Torpedoes mostly into one side, plus bomb strikes. It wasn't going to survive-period. Also worth noting is that Yamato-Class were the first and last ships of their size and were designed in the mid 30s and laid down in the late 30s. Its easy to criticize now but back then they were breaking new grounds of naval technology. Iowa-Class, designed, laid down, and launched, years later still suffered similar flaws and the Japanese didn't have close to the battleship building experience that the US had. The US kept building many ships during the Treaty where the Japanese basically ended their BB fleet expansion.

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Not flooding the bulge was an intentional design decision to allow for more leeway during counter flooding without resorting to further flooding compartments.

Iowa and South Dakota both suffered the same "flaw" in hull plate rigidity.

Apples and oranges. Musashi took the torpedo in the bow outside the protection zone of her torpedo bulkhead. NC took the hit into the bulkhead just forward of the turret which, ironically, still resulted in a penetration of the hull.

The article addresses the very issue of void compartments, in that liquid loaded compartments would actually lessen the effect of a list since those compartments are already filled, and reduces the need for counterflooding. And the SoDak/Iowa lower belt is much more tapered near the keel compared to the Yamato, and the method that the upper and lower belts are joined together is much more robust than seen on Yamato.

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This wasn't a forgone conclusion, it was merely an inherent chance of failure in the design, and it wasn't a "collapse" that was a concern. Its that the joining structure would be pushed inward through the hull from a blast. Yamato took 14-20 (depends on sources) Torpedoes mostly into one side, plus bomb strikes. It wasn't going to survive-period. Also worth noting is that Yamato-Class were the first and last ships of their size and were designed in the mid 30s and laid down in the late 30s. Its easy to criticize now but back then they were breaking new grounds of naval technology. Iowa-Class, designed, laid down, and launched, years later still suffered similar flaws and the Japanese didn't have close to the battleship building experience that the US had. The US kept building many ships during the Treaty where the Japanese basically ended their BB fleet expansion.

It failed when struck by a single submarine torpedo, not just the massive aerial drops that eventually sank it much later. That's where its clear how badly the joint was constructed. It failed to stop even a single torpedo well below the strength the system was designed to take.

The Iowa class's "flawed" TDS (the stories of how "bad" it was are so over exaggerated it isn't even funny). The system was still rated for a 660 lb warhead. North Carolinas system was only rated for 700 lbs, yet withstood 90% of the effect of a warhead packing the equivalent of 893 lb's. The Iowas and South Dakotas should in theory be able to also at least mostly withstand a charge that technically overpowers its rating by nearly 23%, which in this case would be roughly an 800 lb warhead.

Funnily enough, the thing that saved North Carolinas magazine from a possible explosion? It was the 95 mm thick Class B armor plate installed over the magazine spaces. It absorbed most of the force of the explosion that made it through the rest of the TDS without causing splinters or further internal harm. Had a torpedo struck at the same depth on Iowa, it would have had to displace roughly 170 mm of Class B plate, and then cause enough large splinters to pierce the 25 mm bulkhead covering the magazine roughly a meter behind it. Damage may have actually been less on a South Dakota or Iowa, as the explosive force would have been directed upwards and outwards by the belts slope, which would have prevented the extensive damage that North Carolina suffered to its third deck as it blew upwards through the roof of the TDS system.

Whats more is that the liquid loading of the Iowas and South Dakotas is a superior layout to the North Carolinas. The extreme outboard void on the North Carolina essentially does nothing to dissipate the blast of a torpedo striking it, its the three inboard oil loaded layers that do the most work. The Iowa and South Dakotas system has the two outboard layers full of oil, and are the same depth despite having one fewer bulkhead in them. Beyond that is a large void between the lower belt and the liquid layer (important, as this prevents the shock from being transmitted directly from the liquid to the armor plate), followed by another even larger void before the final bulkhead.

Disclaimer: I'm not using this to suggest changes to Yamato in game right now.

Through my Googling, I found a rather interesting article that documents why the Yamato's torpedo defense system was flawed, I pasted the link and article below if you want to open and read the whole thing. But I'll try to provide a TL;DR version.

During the design for Yamato, the decision was made to use reliable, but inefficient boilers and machinery. Consequently, it took 12 boilers to produce the 150,000 SHP that the ship was designed for (compare to 130,000 SHP with 8 boilers on the South Dakota, and 212,000 SHP with 8 boilers on Iowa). Another design driver the Yamato was to make the armored citadel short to save weight, and they accomplished this by arranging the boilers to be 4 abreast of each other in 3 rows, which made the ship very wide. This is why despite the Yamato's large beam, the torpedo defense system depth wasn't actually very high, at around 5.1 m abreast of the machinery spaces, which is actually shallower than North Carolina and Iowa systems.

The second problem with the torpedo defense is that one of the bulkheads of the system is the lower armor belt, since the Yamato had her armor belt extend all the way down to the keel, similar concept to the South Dakota and Iowa. The problem here is that the joint between the upper face hardened belt and the lower homogeneous belt had a very poorly designed, with the traverse shear strength dependent on vertically aligned rivets. Contrast this with the South Dakota (and Iowa) method, where the upper and lower belt are keyed together. Also, unlike the British and Americans, the Yamato's torpedo system did not have any liquid compartments. It's not really clear why the Japanese decided to not do this, the author speculates it may be for lower draft.

Essentially, these problems meant that the Yamato's torpedo defense was not nearly as strong as hoped, and why the Yamato took so much flooding from just one torpedo.

Just before dawn on Christmas day 1943 the Gate class submarine USS Skate was patrolling about 180 nautical miles northwest of Truk. The main operational base of the Japanese Combined Fleet, when her surface search radar picked up three contacts at 23,0(X) yards steaming southeast at 19 knots. As the contacts closed, they showed themselves as one large vessel and two smaller ones, the latter apparently being escorting destroyers. In the growing light of the tropical dawn, Skates Captain, McKinney, dived his boat although he lay to the west in the darkest part of the horizon and fired a salvo of four torpedoes at the largest target. With his submerged speed limited to 10 knots he had no real alternative Course of action and although he was unable to identify it he was rewarded by the gratifying sound of one detonation. However, the ship did not stop and Skate continued her patrol unmolested and unaware that she was the first American vessel privileged to catch sight of the giant battleship Yamato, the pride of the Imperial Japanese Navy.

Such was the parlous state of the Japanese merchant marine, even at this stage of the war, that Yamato had been dispatched as a distinctly unusual fast transport from Truk to Japan on 12 December 1943. She had arrived at Yokosuka with out incident five days later and for the next three days was loaded with supplies and soldiers. With two escorting destroyers she then sailed for Truk and her meeting with Skate. Morison, in his official work on US naval operations in World War II, implied that she was on passage from Truk to Kavieng. In New Ireland when the attack was made but this is incorrect in both the light of Japanese records and the calculations of the distance and time involved.

After the attack, Yamato's speed was unimpaired and she continued on to Truk anchoring later the same day. Eventually, after a vacillating delay of five days, her cargo of troops and stores was off loaded. Any extension of her mission was cancelled. This may well have been a prudent decision because had she completed her sortie she would probably have been attacked by aircraft from two US carriers which were deployed to intercept just such traffic. As her subsequent experiences during the Battle of Leyte Gulf and in the South China Sea demonstrated, she had immense resilience under attack, but such an encounter in a less critical operation would have been, to say the least, ill-judged.

Fortunately, nobody was killed in the attack and as her cargo was being off loaded divers were sent down to inspect the damage and make temporary repairs. Truk had always been more of an anchorage than a fleet base and had few repair facilities, despite allied assumptions to the contrary, and so a return to Japan was inevitable after the torpedo attack. With one escorting destroyer, Fujinami, she sailed from Truk for the last time on 10 January 1944 and docked at Kure six days later. It was to be four months before the damage was repaired and a minor refit completed, though, happily for Japan, she missed no significant action.

Such a catalogue of events is not remarkable. Any ship at sea in wartime is likely to he open to submarine attack and the hit on Yamato was simply one more example to add to many others. What was far more significant for the leaders of the Imperial Japanese Navy was the extent of the damage. The explosion had occurred on the starboard side beneath the after l8in main triple gun turret. Quoting from her Captains report to the Navy Ministry the damage was as follows:

"A hole about 16ft (5m) deep extending downwards from the top of the bulge connection and 82ft (25m) in length between frames 151 and 173. Water flooded into No 3 turret upper magazine from a small hole in the longitudinal bulkhead caused by caving in of the waterline armor"

Put simply, her underwater defenses had been breached by a single torpedo and she had shipped over 3000 tons of water, something which her designers had worked assiduously to avoid. The resultant concern deepened when it was learnt that the torpedo had been running shallow and had struck only four feet below the surface, where the explosive effect, which increases with the depth of water, had not been particularly great. What is interesting is how and why the design failed on a ship which the Japanese had always intended to he the pinnacle of battleship excellence and one certainly capable of stopping a single torpedo. From the time the, Japanese Naval General Staff ordered the Bureau of Naval Construction to study

such a proposal in the autumn of 1934 it was clear the vessel would he enormous since the only sure way of building in superiority in the three key elements of speed, firepower and protection, was to increase the size of the vessel. The first calculations of her principal designers, Yuzura Hiraga and Keiji Fukuda, proved too ambitious even for the Admirals of the Naval General Staff It was speed that was sacrificed since the length and depth of the hull proposed, which were vital prerequisites for high speed, would simply not fit Japanese parts without unacceptable additional expense. On the other hand, a shorter and beamier hull which was still thought likely to confer a speed comparable with future US ships was not without compensations which they did their best to exploit.

Despite this she still had a draft of 10.8m when fully loaded and some dredging was required at the approaches to naval bases and dry docks. Nonetheless, the final trial displacement of 69,100 tons was still close to twice the size of any operational battleship at the time, though the battleships of other navies were naturally following the same inexorable trend, This final design remained, despite the compromise, well balanced. Just over 58 percent of displacement was consumed by the three key considerations:

33.2 percent or 22,895 tons being allocated to armor, 16.9 percent or 11,661 tons to weaponry and 7.7 percent or 5300 tons to machinery. The only slight deviation from what might be thought the norm was that the figure for machinery was a little low, the accompanying reduction in speed required for the weight saved to he used for protection. It is the underwater element of this defense which must now be considered.The ideal of all-round protection had long since been abandoned as shell and torpedo attack had proved too destructive. Along with other navies the Japanese adopted the 'all or nothing' principle; protection was limited to those areas vital for survival and for fighting; in short, the main machinery and gun turrets. The result was an armored central raft which left the bow and stern sections virtually unprotected. The smaller an area this raft represented the stronger could he the armor, and this was not of inconsiderable importance given that a single 12in cube of steel plate weighed a quarter of a ton. In the case of Yamato her great beam, which at the maximum was 127.7ft (38.9m), proved a great boon because her four main turbines and their associated boiler rooms could all be placed side by side across her hull. As a consequence, the area to be shielded shrank to a surprisingly short section of the hull, amounting to just 53.3 percent of the waterline length of 839ft (256m). This was a great achievement and her broad hull also conferred sufficient buoyancy for her to float even if all the unprotected spaces were left open to the sea after enemy action.

Damage from the initial kinetic energy of incoming shellfire could best be minimized by thick armor plate with a hardened exterior, hut such a system could never hope to defeat a torpedo's explosive charge of several hundred pounds detonating in direct contact with it and amplified by the surrounding water. Matters could actually he made worse since the heavy armor tended to fracture and the broken shards could rip deep into the hull. Volume was the best protection against torpedoes since it allowed for the expansion of the explosive gases while the remaining force rapidly dissipated with distance. There was never enough internal volume in a hull to provide much space for this and designers generally had to be satisfied with providing the minimum. In the case of Yamato the constraints were severe despite her great beam because of her chosen machinery layout. This was exacerbated by the choice of a reliable but bulky set of boilers, which ran at relatively low pressure. They were used because replacement beneath the 200mm armored deck would have proved extremely difficult hut the corollary was a narrower torpedo defense.

The width of this around her machinery spaces was on average 5.1m, and was narrower than that of almost all her contemporaries in other navies despite her displacing considerably more. Two examples will suffice to illustrate this. The American North Carolina, on a displacement calculated in a comparable manner at 45,298 tons, had a system 5.6m deep, while the German Scharnhorst on only 35,398 tons still managed a depth of 5.4m. For Yamato, it was therefore essential that within the comparatively narrow space remaining the best possible arrangement was used.

In order to counter a torpedo explosion, a space outside the true hull was required which would be strong enough to detonate the weapon well away from a stronger yet flexible main bulkhead beneath. The Japanese developed empirical formulae to determine the thickness of protective bulkheads and bulges based on tests with models and full scale systems. Once established they were then used with much confidence and for Yamato the main bulkhead was to be 75mm ducol steel. When a full scale plate of this was duly tested in 1939 against a blast of 400kg of TNT, the results were encouraging since it did not split open although its watertight integrity was lost.

Unfortunately, the designers also had to counter what was considered to be the great danger of long range plunging shell fire which might dive under the main armor belt and into the ship's vitals. The physical requirements for resisting the kinetic energy of shellfire and the explosive force of torpedoes could not be easily reconciled in a single system, but in Yamato there was not the room to separate one from the other. The enormous 410mm main belt was inclined on average at a 20 degree angle which increased the thickness of armor which any steeply falling shell would have to penetrate, and this angle conveniently provided space outboard for the anti-torpedo bulge without altering the form of the hull. The belt would have run into the 75mm anti-torpedo bulkhead below, but such was the fear of shell fire following tests on the underwater trajectories of projectiles that this was radically increased in thickness till, over the main machinery, it tapered from no less than 200mm down to the original 75mm at the ship's bottom.

Given a larger bulge outboard this main defense would have been far more formidable but by linking it to the main belt the bulge was only 3m wide at most at mid-draft. By comparison with foreign practice this placed it uncomfortably far forward thus failing to take full advantage of the limited depth available and compounding the weakness by reducing its ability to deform under pressure, just when such a feature was more essential. In the USN, the South Dakotas had a similar arrangement but they were designed within stringent Treaty constraints, a worry Yamato's designers did not have. In the US Montana class, a planned vessel of similar dimension to Yamato, the holding bulkhead was placed much deeper and not tied to the belt at all.

This late adoption of a thicker, lower bulkhead caused a new problem: how to join it to the main belt above without jeopardizing the great inherent strength of either half. The solution, as can be seen, was far too flimsy and relied for its transverse strength, which would be tested most in a torpedo strike, on the shearing resistance of tap and three-ply rivets. This was to prove the Achilles heel of the system.

The percentage of explosive force which would break on this flawed main defense did not rely only on the volume of the intervening outboard space. The composition of this space could be significant, and in all Yamato's foreign contemporaries part or all of the outboard void was tilled with liquid, generally fuel oil. This was not a fire risk and since it was incompressible it could spread and reduce the shock of any explosion, and in addition diminish the danger from splinters. The Imperial Navy were well aware of this system and thought liquid layers next to the main bulkhead were the best type, but like the Royal Navy, their primary teachers, they also experimented with using closed steel tubes which were packed into the outboard spaces to fulfill a similar function.

In practice they rusted and proved inefficient energy absorbers although in a Japanese report of 1936 their use was calculated to reduce 'the thickness of the protective plate to 70 percent generally'. For Yamato, even this expedient was dispensed with partly because of the chronic steel shortage exacerbated in large measure by her and her sister's construction, Although fuel oil was stored in the double bottom this was the only use of liquid and its defensive properties were not taken into any calculation. Yamato's outboard explosion chambers were left watertight and empty of anything more tangible than air.

Since the advantages of liquid loading were understood, this result is difficult to comprehend, despite assertions at the time that the heavy armor would be sufficient by itself. Pumping arrangements for such spaces could increase flooding since the valves between tanks were liable to fracture after an explosion. but since Yamato ~ range of 7200 nautical miles at 16 knots was low, taking into account the vast size of the Pacific. the extra storage would have proved beneficial in more senses than one. It has also been suggested that they needed to he left empty for possible use in counter flooding, and they were certainly equipped for this, and yet if they were partially filled, flooding with seawater on one side would have had less effect. It is possible that the need to keep her draft shallow influenced the decision. This is supported by the fact that a proposal to reduce the individual volume of compartments outside the citadel was rejected because the extra weight would have had an adverse effect on her draft.

Two longitudinal bulkheads were included between the main armor and the outboard main machinery spaces in order to contain any flooding and, in addition, the anti-torpedo bulkhead was thickened, The two bulkheads were designed to be capable of deforming without rupturing and, to add elasticity, the flooring was offset on opposite sides of the bulkhead, hut it was still too stiff and it could suffer little deflection without rupture, at least of butts and floor connections'. There was also a fear that because the fire rooms were closed, the air pressure inside the boiler rooms would he too great, and so the two inner defenses were braced still more by heavy beams placed transversely at the upper operating level. Any movement of the bulkheads, however, would simply cause them to be punctured by the beams permitting water to enter the fire rooms. Opposite the magazines forward and aft of the machinery such expedients were not required but there was only one holding bulkhead behind the main armor, reflecting the narrowing of the hull which confined internal volume still more. If this last over-rigid barrier was breached, internal flooding was inevitable.

This, in essence, is what happened when Skate's torpedo struck. Running shallow it hit the bulge where it was less than 2m wide and the main belt took most of the blast.

This did not fracture, hut the weak joint below did shear, indenting both sides into the ship by about I m. This in turn led to the last defense being holed as mentioned in her Captain's report. Had the torpedo been running deeper and hit closer to the suspect joint, damage would have been far greater. The resultant flooding caused a list of two to three degrees hut since the outboard voids were fitted with sea [edited] of 10in diameter, which could be operated remotely, counter flooding on the port side quickly put her hack on an even keel.

When these weaknesses were realized by the technical teams investigating the damage, they suggested that a new plate be installed across the lower corner of the upper void between the two inboard bulkheads and inclined at 40 degrees. This was proposed for the full length of the machinery spaces but it was hopelessly inadequate and in the event was only fitted in the region that had been damaged.

Of greater interest are the factors surrounding the decision taken in 1939 to increase the armor thickness of the side defenses, and accept what was always suspected to be a weak joint between it and the main belt. The importance of Yamato in prewar Japanese naval plans cannot he overestimated. The state economy could not hope to compete with that (if the USA in quantity, so quality and superior technology were, not for the first or last time, seen as the solution, and Yamato was the embodiment of this ambition. The navy had already constructed an elaborate and detailed plan to defeat the US Pacific Fleet, and it was intended that the big guns of the Combined Fleet would deliver the loop de grace. This planned scenario does much to explain why Yamato's designers changed emphasis towards favoring an anti-shell protective defense.

The unwillingness to wait for a suitable joint to he developed can also be understood in relation to the Imperial Navy's overall plans for the future. To establish her necessary technological lead, secrecy was vital to forestall any American response, but despite inordinate Japanese zeal some rumor of what was happening inevitably crossed the Pacific'. The US had, therefore, recommenced naval building and any delay in the construction of Yamatowould have sacrificed the Imperial Navy's slender lead.

Rivalry between the army and navy also played its part, not only over funding such items as expensive battleships, hut also in determining national policy. In such a climate delays in construction could have given the army the upper hand and so had to he avoided.

Two major ironies overhang this discussion. The obvious one is that all this time, effort and money spent on battleship construction was to prove virtually irrelevant. The future of naval warfare lay with carrier air power not the big gun. Both Yamato and her sister Musashi were to succumb to aerial attack, their main 18in guns virtually unused in anger. The second is that the torpedo fired by Skate was armed with a warhead of 635lb of a new explosive,'Torpex'. This had twice the explosive power of TNT and with its introduction in 1943 it upset, at a stroke. all the careful calculations on which Yamato's designers had labored for so long. It will be recalled that constraints were such that defenses could only ever he just sufficient: With the introduction of Torpex the most robust anti-torpedo system was likely to be breached. It was a pity that Yamato's design sacrificed underwater defense in depth when the threat in this sphere had increased so markedly. Nonetheless, even with the flaws discussed here her defenses were still powerful and her resilience under assault later amazed her American foes. However, her torpedo protection was without doubt the weakest element in an impressive design and it is not surprising that torpedoes were eventually to dispatch both vessels.

Nothing personal but nothing new. Most Japanese ships had Torpedo flaws IRL but as normal Devs and such do lack luster research or only use material they can get from the shelf look what happen to most western ships. Only Effective Torpedo Defenses that I now of where on American,German and British ship designs. The French on paper also looked good but most of there fleet was sunk at Mers-el-Kébir to prevent theme from falling into anyone's hands to be seen in combat effectiveness.

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It failed when struck by a single submarine torpedo, not just the massive aerial drops that eventually sank it much later. That's where its clear how badly the joint was constructed. It failed to stop even a single torpedo well below the strength the system was designed to take.

I take it you don't know they further reinforced these areas along the entire length of the Citadel of Yamato during a dry dock.

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I take it you don't know they further reinforced these areas along the entire length of the Citadel of Yamato during a dry dock.

No he doesn't did the same as the company assumed something instead of research but over all the Japanese Torpedo defenses where that good compared to other Navies of the time. They wernt a failure but where not as good either.

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I take it you don't know they further reinforced these areas along the entire length of the Citadel of Yamato during a dry dock.

Nice try, but no. They further reinforced the system to an extent, but they didn't even follow through with their own recommendations. To quote what they did exactly;

16 January 1944:
Arrives at Kure. Later, YAMATO is docked in No. 4 drydock to repair the torpedo damage to her hull and correct deficiencies in her armor belt. A sloping plate is fitted at a 45-degree angle across the lower corner of the upper void compartment between the two longitudinal inboard bulkheads. This modification, proposed to run the full length of the citadel, is installed only in YAMATO in the area affected by torpedo damage.

Also:

In the event, the measure was inadequate. A recommendation to use 5,000 tons of steel to reduce the volume of compartments beyond the citadel and so increase resistance to flooding was rejected because the extra weight would have increased displacement and draft beyond acceptable limits.

It solved literally none of the problems that had caused it to fail in the first place. The simple fact of the mater is that the system is too shallow, has no liquid loaded layers to absorb shock, and has zero deformable bulkheads at any point. The two key factors for a good TDS are depth, and liquid/void division. Yamato had neither, in addition to the faulty joint that was never truly solved in any manner.

As near as anyone can tell, it failed every single time it was struck by an aerial torpedo during the final battle. The only thing that kept them afloat for so long was the honeycomb of internal compartments that limited the extent of the flooding from each separate failure. Even with that, they were still forced to intentionally flood machinery spaces in an attempt to stabilize the ship. Something similar happened during Bismarcks sinking, where torpedo strikes on the opposite side of the ship actually managed to counterflood her somewhat, delaying her demise. Musashi may have taken 19 (closer to 11 by the Japanese report) torpedoes and stayed afloat for six hours, but it didn't take 19 torpedoes to kill her. By about the 8-9th torpedo hit, the flooding was unstoppable, the damage too extreme. An American carrier, Yorktown, took four torpedoes, several bombs, and 500 5" shells and stayed afloat for twelve hours after she had been completely abandoned. That doesn't mean she wasn't doomed the instant flooding overtook the damage control efforts.

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I take it you don't know they further reinforced these areas along the entire length of the Citadel of Yamato during a dry dock.

Did you even read the article? Based on records the author concluded that they only reinforced the area that was damaged and then repaired.

As for the SoDak and Iowa torpedo systems, it has the same concerns that the lower belt may be too rigid to elastically deform and absorb energy, but looking at material properties of Class B shows that it has a % elongation of 25%, which is actually a bit more than HTS average of 22%. My hypothesis is that it may be the connection between the belt and the keel that is suspect, since Class B is quite a bit stronger than HTS.

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Did you even read the article? Based on records the author concluded that they only reinforced the area that was damaged and then repaired.

As for the SoDak and Iowa torpedo systems, it has the same concerns that the lower belt may be too rigid to elastically deform and absorb energy, but looking at material properties of Class B shows that it has a % elongation of 25%, which is actually a bit more than HTS average of 22%. My hypothesis is that it may be the connection between the belt and the keel that is suspect, since Class B is quite a bit stronger than HTS.

Looking at the B armor plate on NC's magazine, it seems to have dished inwards rather cleanly. The same would probably occur to a lesser extent on Iowa/SD because of the increased thickness and attachment method of the plate to the structure, with the real threat being the lower edge potentially compromising the hull (it was to my understanding that it should have ended slightly higher up, rather than continuing to taper to the top of the triple bottom). I can't imagine it causing nearly the same level of catastrophic failure as was present in Yamatos case though.

Most Japanese sources I've seen list 11 torpedo hits, ten bombs and six near misses. That could be totally outdated information though, as I know they only recently found the wreck itself.

The most authoritative source we have in writing, and that will likely never change, is the "Detailed Battle Report #4." It is the only source we have that details not only numbers of hits, but also locations right down to the frame numbers. That is then backed up with the relevant sections of the Senshi Sosho. Of course actual confirmation through surveying the wreck is a whole different matter. That could (or could not) change lots of things.

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The most authoritative source we have in writing, and that will likely never change, is the "Detailed Battle Report #4." It is the only source we have that details not only numbers of hits, but also locations right down to the frame numbers. That is then backed up with the relevant sections of the Senshi Sosho. Of course actual confirmation through surveying the wreck is a whole different matter. That could (or could not) change lots of things.

It's to my understanding that almost the entire center of the ship was obliterated by an explosion and created a massive debris field, which probably wiped out any evidence there. Drawing's I've seen of the wreck have most of the hull from the B turrets barbette >forward in relatively whole condition, with at least one torpedo strike noted on the port side, the starboard side resting in the sea floor. The entire aft of the ship looks like it twisted and landed mostly upside down in one big piece.

I guess wishing for a Bismarck style wreck where the hull is basically intact and resting upright was a bit much to hope for

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The manner in which the lower belt section was constructed and attached to the structure of the hull precluded the same total failure and collapse as happened with Yamato's system.

Actually, looking at how the SoDak and Iowa upper and lower belts are keyed together while sharing backing plates, it seems true that this keying makes the joint much stronger in shear, but if they're only keyed together, then they would not offer any strength in bending since there's nothing holding the two belts together in the tensile vertical direction; bending would depend all on the backing plate.

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Did you even read the article? Based on records the author concluded that they only reinforced the area that was damaged and then repaired.

Okay, read, and while you were happy to jump in above about deficiencies you never pointed out to spud the last paragraph stating that the Torpedo fired by Skate had the TNT equivalent of between 1000-1200lb which almost assuredly would of defeated any TDS of the time.